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Papaya is grown from seed. Germination is epigeal and takes 2-3 weeks. Seedlings grow rapidly. Since their sex cannot be determined before flowering, normal practice is to plant 3-5 seedlings together and retain only the most vigorous hermaphrodite or female plant at flowering. With controlled pollination, the ratios of female, hermaphrodite and male offspring are predictable:
*female × male →→→➞ → 1 female : 1 male;
*female × hermaphrodite -> → 1 female : 1 hermaphrodite;
*hermaphrodite × male -> → 1 female : 1 hermaphrodite : 1 male.
Thus in some combinations all resulting plants should bear fruit. Pollination is basically by wind and aided by small insects like thrips.
== Diseases and pests ==
Damping-off is caused by the soilborne fungi ''Phytophthora parasitica'' , ''P. palmivora'' and ''Pythium aphanidermatum'' . Phytophthora also occurs in the orchard, infecting both the trunk and the fruit. Good aeration, drainage, and hygiene are important to curb these fungi in the orchard as well as in the nursery. It is advisable not to replant papaya on the same land. Anthracnose, caused by ''Glomerella cingulata'' (imperfect form: ''Colletotrichum gloeosporioides'' ), primarily infects the fruit. The disease appears as small water-soaked circular spots that enlarge into brown-black sunken lesions as the fruit ripens. Fungicidal spray at 7-10-day intervals can control this disease. A 20-minute hot water dip (45°C) reduces post-harvest decay.
Papaya ringspot is a devastating virus disease that was detected in the Philippines in 1982. It had earlier caused considerable losses in Hawaii, Florida and Taiwan. Initially, the disease appears as oil streaks on stems and petioles and as it progresses, mottling of leaves becomes evident. Severely infected plants do not flower and die young. The virus is transmitted by aphids. Control measures are planting in isolation, removing and destroying infected plants, and using tolerant cultivars. Cross-protection has been advocated, but this requires the availability of a mild virus strain for inoculation of seedlings. Mosaic is another virus disease transmitted by aphids, and bunchy top is caused by a mycoplasma transmitted by a hopper.
Rootknot ( ''Meloidogyne incognita'' ) and reniform ( ''Rotylenchulus reniformis'' ) nematodes infest papaya. Feeding nematodes cause root swellings or root galls, resulting in yellowing and premature abscission of the leaves. Since nematicide treatments are expensive, it is important to use clean land, not replanting papaya in the same field.
The oriental fruit fly ( ''Dacus dorsalis'' ) is a major concern of papaya- importing countries such as Japan and the United States. The flies deposit their eggs in ripe fruit. Fruit should be harvested at the mature green stage. Over-ripe and infested fruit should be buried. Male flies can be baited by placing a cotton ball dipped in methyl eugenol-malathion solution inside trap bottles positioned every 25 m throughout the plantation.
Mites ( ''Tetranychus kansawai'' and ''Brevipalpus californicus'' ) suck the plant sap, leading to poor plant growth and blemishes on the fruit. Predatory mites generally provide adequate control, an additional reason for restraint in the use of acaricides or insecticides with miticidal action. Aphid ( ''Aphis gossypii'' , ''Myzus persicae'' ) infestation weakens the plants and aphids also transmit virus diseases. Removing alternative hosts and the presence of natural predators can effectively reduce aphid populations. Spraying insecticide on the undersides of the leaves is also an effective control measure.
== Harvesting ==
== Literature ==
* Abdon, A.C., 1980. Food composition tables recommended for use in the Philippines. 5th revised edition. Food and Nutrition Research Institute, Manila. 313 pp.
* PCARRD, 1984. The Philippines recommends for papaya. Los Baños, Laguna. 58 pp.
* Storey, W.B., 1969. Papaya (Carica papaya L.). In: Ferwerda, F.P. & Wit, F. (Editors): Outlines of perennial crop breeding in the tropics. H. Veenman en Zonen BV, Wageningen. pp. 389-407.
== Authors ==
